1. Field of the Invention
The invention relates to a motor arrangement with an electronically commutated electric motor of an explosion-protected configuration, as they can be found, for example, in applications for driving fans in a potentially explosive atmosphere.
2. Description of the Related Art
In such motor arrangements, so-called safety barriers are conventionally used which, however, are too expensive for most applications. Also, voltage drops that are too high can occur for such safety barriers.
It is an object of the present invention to provide a new motor arrangement whose motor is suitable for operation in a potentially explosive environment.
In accordance with the present invention, this is achieved in that on the stator of the electric motor, and separated from the permanent magnetic motor by an air gap, at least one galvanomagnetic rotor position sensor is provided for detecting a magnetic field of the permanent magnetic motor whose output signal serves for controlling an electronic commutation device; the current supply of the galvanomagnetic rotor position sensor is realized by an alternating-current (ac) or three-phase current supply system with interconnection of an isolation transformer; and the output signal of the galvanomagnetic sensor is supplied via an opto-coupler to the electronic commutation device.
In a motor arrangement according to the invention an electric motor with a galvanomagnetic sensor is thus used. Between the motor circuit and the sensor circuit a complete electrical isolation is provided by which it is reliably prevented that in a failure situation energy-rich mains voltage can reach the sensor circuit. The actual electronic commutation device of the motor arrangement is preferably arranged external to the electric motor. This makes it possible to electrically separate (isolate) the sensor circuit completely from the coil circuit of the electric motor, for example, on a relatively small printed circuit board mounted within the electric motor. Since the output signal of the sensor is supplied by an opto-coupler to the electronic commutation device, a complete electrical isolation is possible also in this context.